This invention relates to a multi-cylinder internal-combustion engine with a swinging piston.
FRG Patent No. 1,601,818 and U.S. Pat. No. 3,388,963 to James disclosed a swinging-piston, supposedly two-cylinder gasoline engine with a connecting rod and crank mechanism and spark plugs for ignition. In that design, the swinging piston actually forms four cylinders, the top two of which are for admission and compression and, therefore, act as scavenger pumps, and the bottom two of which are operating cylinders. The engine works on the principle of two-stroke cycles. It has, however, the following disadvantages:
1. The problem of scavenging between the admission and compression cylinders and the operating cylinders has not been solved properly. Three types of scavenging structures are used therein: air valves and springs and two others. Using air valves and springs to form an automatic valve to control air intake requires a complicated structure and great mass. Further, an engine having such a valve system can only be operated at lower speeds. Furthermore, the valve system cannot be applied to a reciprocating air compressor, because the pressure loss of the air motion is too large to be acceptable. The other two structures, using intake port scavenging, have some troubles in air sealing, which cause lower efficiency of the engine and make it operate improperly, owing to too much air leakage.
2. The exhaust gas from the operating cylinders has not been properly taken into account. In every working stroke, the exhaust ports communicate with the crankcase, and as a result, the lubricating oil in the crank case is polluted by the exhaust gases and part of the lubricating oil is carried away through the exhaust pipe.
3. The admission and compression cylinders use one, common admission port, which is located at the middle of the cylinders, and the effective stroke of air intake in each cycle is, therefore, short. The air intake amount is, therefore, too small to meet the demand of the operating cylinders, resulting in much lower power and efficiency of the engine. If supercharging were adopted and compressed air were led into the admission port, the top part structure of the engine would be unnecessary.
4. Finally, some parts of the engine cannot be made strong enough; specifically, the swinging-piston sealing and cooling devices.
In French patent No. 2,375,439, a swinging-piston and connecting-rod crank mechanism is proposed wherein the swinging piston forms four cylinders, the top two being operating ones, and the bottom two being admission and compression ones which act as scavenger pumps. In the swinging piston, there are intake ports, which intake air automatically from outside and form uniflow scavenging for the operating cylinders. This results in double-cylinder, two-stroke operation, whereby the engine can work at higher speeds. The disadvantage of this is, however, that the effective stroke is so short that the efficiency of the engine is greatly lowered. Moreover, since the crankcase communicates with the admission cylinders, a large amount of lubricating oil can be brought into the operating cylinders.